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264-11 Icehouse Conditions Significantly Predated The End-Ordovician Mass Extinction
Session: Integrated Stratigraphic, Geochemical, and Paleobiologic Perspectives on Earth System Evolution: A Session in Honor of the Contributions of Bradley B. Sageman (Part II)
Presenting Author:
Xiaoli MA
Authors:
MA, Xiaoli1, Marshall, Charles R.2, Montañez, Isabel P.3, Fan, Junxuan4r>
(1) School of Earth Sciences and Engineering and Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing, Jiangsu, China; State Key Laboratory for Mineral Deposits Research, Nanjing University, Nanjing, Jiangsu, China, (2) Department of Integrative Biology and University of California Museum of Paleontology, University of California, Berkeley, Berkeley, California, USA, (3) Department of Earth and Planetary Sciences, University of California, Davis, Davis, California, USA; Institute of the Environment, University of California, Davis, Davis, California, USA, (4) School of Earth Sciences and Engineering and Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing, Jiangsu, China; State Key Laboratory for Mineral Deposits Research, Nanjing University, Nanjing, Jiangsu, China,
Abstract:
The severe end-Ordovician glaciation likely played a major role in the end-Ordovician mass extinction. An open question is the extent to which icehouse conditions preceded this glaciation. Here, we document the latitudinal temperature gradients using carbonate oxygen-isotope paleothermometers (3,405 well-screened proxy values) to constrain the equatorial temperatures and steepness of the gradients through the Ordovician. We show that temperatures crossed the threshold to icehouse conditions ~13 Myr before the end-Ordovician extinction (~Darriwilian-Sandbian boundary) with a temperature gradient similar to the Last Glacial Maximum. We find even colder temperatures and a steeper LTG at the end of the Ordovician. The Ordovician, with a transition from extreme hothouse conditions to severe glaciation, likely driven by tectonics-driven pCO2 drawdown, coupled with biodiversity changes, provides an ideal time interval for examining the relationship between environmental change and biodiversity.
Geological Society of America Abstracts with Programs. Vol. 58, No. 5, 2026